1. Field of the Invention
The present invention relates to optical cavities that provide coherent superposition of optical pulses and that focus the optical pulses into a localized interaction region. Such optical cavities may be used, for example, to produce x-ray and gamma-ray emission from Compton backscattering of optical photons from high energy electrons.
2. Description of the Related Art
In many technological areas there is a need for a system for accumulating optical energy by coherently superimposing laser pulses in order to generate high intensity optical pulses that are focused onto a localized interaction region.
For example, various research endeavors in fields such as atomic and molecular physics, x-ray crystallography, proteomics and genomics, nuclear spectroscopy, and astrophysics require the production of x-ray or gamma-ray beams having high photon fluences. One method of generating such x-rays and gamma-rays is to direct high energy electrons into a region illuminated by optical photons. Energy from the electrons is imparted onto the photons via Compton backscattering, thereby producing higher energy photons such as x-rays and gamma-rays. The intensity of the x-ray and gamma-ray output is directly dependent on the quantity of photons that interact with the electrons. Accordingly, to achieve the desired high photon fluences of x-rays and gamma-rays, high intensity optical pulses with correspondingly large photon counts are preferably interacted with the high energy electrons. To produce such high intensity optical pulses, a pump laser is arranged to emit laser pulses into an optical cavity having a cavity length suitable for providing coherent superposition of the laser pulses. The intensity of the optical pulses within the cavity depends in part on the number of laser pulses that are coherently stacked. The intensity of the optical pulses is further enhanced by focusing the optical output into a small localized region where the optical pulses interact with the electrons.
The study of laser-matter interactions may also benefit from optical systems configured to focus high intensity optical pulses into a small localized region. Interesting interactions between atoms, molecules, and other matter can occur in a localized region having high electromagnetic field strength. To introduce large amounts of the optical energy into the interaction region thereby producing enhanced strength electromagnetic fields, it is advantageous to have the capability to focus and precisely aim high intensity optical pulses.
What is needed therefore is an optical storage cavity in which optical energy within the cavity can be accumulated by coherently stacking laser pulses emitted from a pump laser. It is further desirable to configure the optical cavity to produce a narrow focal spot at a localized interaction region, e.g., within the cavity. The system preferably also should minimize the loss of optical energy from the cavity in order to achieve high efficiency.